A gillnet is known as a type of fishing net. It has been empirically known that a fish haul is varied depending on the coloration of such a gillnet. Accordingly, by adopting such gillnet colors as hardly visible to fish, a fish haul improvement can be achieved. However, the colors hardly visible to fish are varied depending on the variation of the color of the sea bottom and the variation of the sunlight. Thus, gillnets are often dyed by the fishery workers, on the basis of the fishery workers' experiences in such colors that are hardly visible to fish in the waters where fishing is conducted. Specifically, the fishery workers purchase monochromatic fishing nets and the fishing nets are dyed by the fishery workers themselves, and thus the fish haul improvement is achieved.
Alternatively, fishing net manufacturers, at the manufacturing stage of the fishing nets, vary the color horizontally, namely, in the lengthwise directions of the fishing nets on the basis of the demands of fishery workers. This color variation is referred to as “paneling.” In this technique, along the lengthwise direction of a fishing net, which is the same as the mechanical fishing-net knitting direction, the fishing net is cut into sections each having a predetermined length much longer than the widthwise length thereof, the thus cut respective sections of the fishing net are dyed separately, and finally, the respective dyed sections of the fishing net are joined by hand sewing to complete the fishing net. In general, the number of the meshes joined in this case is about 30 to 120, and consequently, the cost increase in the production of a fishing net, ascribable to this cutting and joining process, accounts for about a few percent of the product price. Practically, a fishing net is about 2.5 to 15 m in width and 200 to 1200 m in length.
A technique for varying the color from section to section is described in U.S. Pat. No. 5,819,464. In this technique, the respective sections of a fishing net are dyed with different dyes varying in color from section to section, and accordingly it is possible to give different colors in the water depth direction, namely, in the widthwise direction of the fishing net. In this way, as compared to the case where the color is varied solely in the lengthwise direction of a fishing net, the fish haul may be expected to be further improved.
However, the method of U.S. Pat. No. 5,819,464 takes considerable time and labor, because as described above the respective sections of a fishing net are dyed with different dyes varying in color from section to section, and accordingly dyeing is required to be repeated the same times as the number of the colors. Additionally, aside from the number of the colors, the process of dyeing the respective sections of a fishing net with dyes varying in color from section to section also takes considerable time and labor because such a process requires, for example, to select one of the respective sections from the one continuously formed fishing net and to dye the particular selected section at a time.